Trifluoroethylene (CHF═CF2) is a known compound used as a monomer in the preparation of various fluorinated polymers. Trifluoroethylene is a gas at ambient temperature. The storage and transportation of trifluoroethylene poses a number of safety issues in view of its tendency to violently deflagrate, see for instance FEIRING, A. E., et al. Trifluoroethylene deflagration. Chemical&Engineering News. 1997, vol. 75, no. 51, p. 6.
Trifluoroethylene is known to disproportionate with liberation of great amounts of heat resulting in a significant pressure rise and explosion. The disproportionation reaction can be triggered by the polymerization of trifluoroethylene which occurs spontaneously. For this reason polymerization inhibitors, such as limonene, are generally added in amounts of up to 5% by weight to trifluoroethylene. However polymerization inhibitors do not render trifluoroethylene stable, they only remove a potential source of ignition. Thus, the presence of known polymerization inhibitors is not sufficient to eliminate the deflagration hazard connected with the storage and transportation of trifluoroethylene, see FEIRING, A. E., et al. Trifluoroethylene deflagration. Chemical&Engineering News. 1997, vol. 75, no. 51, p. 6.
Although trifluoroethylene can be liquefied by sufficient pressurization in a container, storage and transportation of trifluoroethylene as a liquid is generally avoided because of the risks of explosion of the gas in equilibrium with the liquid (the gas phase may contain not enough polymerization inhibitor because the inhibitor is less volatile than trifluoroethylene). Thus, as a precaution, liquid trifluoroethylene is generally kept below −30° C. and its quantity is kept to the minimum required for the process. On the other hand a stable gas phase in equilibrium with a liquid phase would reduce the risk of ignition of the liquid phase itself, as deflagration of the liquid is usually possible only after ignition of the gas phase.
Studies with trifluoroethylene in the gas phase indicate that there is a reduced risk of disproportionation at pressures below 0.35 MPa. As pressure increases above this value, the risk of disproportionation and, consequently, deflagration increases. For this reason trifluoroethylene is generally stored, handled and transported at pressures not exceeding 0.30 MPa. The amount of trifluoroethylene transported per unit volume is thus very limited with a great impact on the cost of this material. The safety and consequently, cost issues related to the storage and transportation of trifluoroethylene are such to limit the use of trifluoroethylene as a monomer regardless of the potential economic interest of the polymers obtainable therefrom (see for instance WANG, Z., et al. High dielectric VDF/TrFE/CTFE terpolymers prepared by hydrogenation of VDF/CTFE copolymers: synthesis and characterization. Macromolecules. 2006, vol. 39, p. 4268-4271.).
Thus the need exist for means of safely storing and transporting trifluoroethylene.